1. Field of the Invention
The present invention pertains to an improved method of plugging perforations and other wellbore void spaces by squeeze cementing after placement of a cement retaining material such as a resin-coated proppant in the spaces to be occupied by the cement.
2. Background
In wellbore cementing operations, it is conventional practice to plug perforations and re-cement casing by a technique commonly known as squeeze cementing. In squeeze cementing, a column of cement is forced under pressure against the formation through the perforations to be plugged or by circulating cement under pressure into a wellbore void or space which is to be filled to secure wellbore structures, stop lost circulation or plug off particular portions of the wellbore. In plugging off perforations and other spaces, particularly in deviated or near-horizontal wellbores, it has been discovered that the location or configuration of the void or space, such as a so-called perforation tunnel, to be filled with cement may be such that, once the cement pressure has been relieved and the cement washed from the wellbore, cement will drain back out of the perforation tunnels or other spaces into the wellbore, thereby failing to form the plug or closure desired.
For example, in deviated or near-horizontal production wells, when a particular production zone has been depleted and it is desired to close the perforations and the perforation tunnels in the formation, the tunnels themselves may have grown substantially due to production of sand along with the fluid flowing from the formation into the wellbore. Accordingly, it is difficult to force enough cement into the expanded perforation tunnel which will solidify and place the depleted zone of the formation in a substantially fluid-impermeable condition. It is indicated from unsuccessful squeeze cementing operations that when cement is removed from the wellbore, at least some of the cement in the expanded perforation tunnel or other space in communication with the wellbore will flow back into the wellbore, thereby defeating the intended plugging effort.
It is contemplated that efforts to abandon non-productive or depleted zones, supplement faulty primary cementing jobs, isolate zones before perforating, repair defects such as joint leaks, split or parted casings and stop lost circulation also experience the same problems, in vertical as well as deviated or near-horizontal wellbores where force of gravity or formation pressures will force cement out of a space which it is intended for the cement to occupy. However, the present invention overcomes these problems in cementing wellbore perforation tunnels and other wellbore spaces as will be appreciated by those skilled in the art upon reading the following summary, detailed description and claims.